Polyamide and polyolefin blends with a polyamide matrix and containing nanofillers

ABSTRACT

The present invention relates to polyamide (A) and polyolefin (B) blends containing nanofillers in which the polyamide forms the matrix. These blends can also be referred to as “polyamide (A), polyolefin (B) and nanofiller blends in which the polyamide forms the matrix”. The invention also relates to structures with barrier properties comprising at least one layer of these blends and optionally at least one layer of another material. These structures are a barrier to numerous fluids, and in particular to oxygen, to styrene, to fumigation fluids, to pentane and to air conditioning fluids. These structures can be made into bottles, reservoirs, containers, pipes and vessels of all sorts. They can also be converted to films which are used to make packagings.

This application is a divisional of Ser. No. 10/803,008, filed Mar. 17,2004, now U.S. 7,029,735, which claims priority from ProvisionalApplication 60/508,965, filed Oct. 6, 2003.

FIELD OF THE INVENTION

The present invention relates to polyamide and polyolefin blends with apolyamide matrix and containing nanofillers. These blends arethermoplastic and can be converted to bottles, reservoirs, containers,pipes and vessels of all sorts. They can also be converted to filmswhich are used to make packagings. The invention also relates tostructures comprising at least one layer of these blends and at leastone layer of another material. These structures can be converted tobottles, reservoirs, containers, pipes and vessels of all sorts. Theycan also be converted to films which are used to make packagings.

All these objects exhibit good barrier properties. The invention alsorelates to the use of these objects. For example, foods packaged inthese packagings are protected from atmospheric oxygen and theirdegradation is avoided, whereas a polyethylene packaging allows someoxygen to pass through and the foods undergo degradation. The barrierproperties can also be used in another sense. Thus, in the SMC(abreviation of Sheet Moulding Compound) technology, a composition basedon crosslinkable unsaturated polyester and on styrene is disposedbetween two films and it is necessary for the styrene to remain in thecomposition and not to diffuse through the films. It is also possible tomention the barrier to pentane which is useful in packagings containingexpandable polystryrene beads. Indeed, these beads contain pentane andit is necessary that the beads do not lose their pentane before theirconversion to expanded polystyrene. It is also possible to mention pipesin which the cryogenic fluids for air conditioning circulate, such asfor example HFAs and HFCs. In an air conditioning device, loss of fluidshould be reduced both for economic reasons (these fluids are expensive)and for environmental protection reasons (an excessive leakage coulddamage the ozone layer). The structures of the invention are useful inthese applications.

BACKGROUND OF THE INVENTION

SMC is used in the manufacture of converted articles not only in theautomotive field (bumpers, tailgates, etc) but also in the marine (boathulls) or electronics (casings) fields. SMC is generally composed of acrosslinkable polymeric resin, in particular an unsaturated polyester,reinforcing fillers such as glass fibres, and various other additives inminor quantities.

The SMC is ordinarily prepared by laying fibres on a layer ofunsaturated polyester resin, which is itself supported on a moveablefilm, composed in general of polyethylene or of polyamide. Another filmof the same kind is subsequently laid over the resin/reinforcing fillersystem in order to form a sandwich composite structure between twofilms. The sandwich subsequently passes through a series of kneading andcompacting rollers and is generally wound up in the form of large rolls.

It is then stored before subsequent forming. During the storage period,the polyester resin undergoes partial crosslinking, which brings aboutan increase in the viscosity of the SMC, until it attains a consistencymaking it suitable for moulding. SMC users, generally moulders, cut anappropriately sized section from the roll, remove the support film bypeeling and place the SMC in a heated mould for simultaneous forming andfull cure. Thus composite compounds in the form of an SMC sandwich findready application in compression moulding procedures.

The BMC (Bulk Moulding Compound) technology is similar except that thepolyester to be crosslinked is either in a thick layer between two filmsor is in bulk in a drum packed with a film. The SMC and BMC compositionscontain styrene.

Three properties relating to the sandwich film are of crucial importancefor SMC manufacturers and users.

The first relates to the permeability of the peelable film to styrene.It is necessary for this peelable film to have a very low permeabilityto styrene in order to avoid the loss of monomeric styrene which playsthe role of crosslinking agent in SMC. This loss of monomeric styrene isalso damaging for the health of individuals and for the environmentduring operations for the manufacture of SMC and for its storage.

The second property relates to the ease of peeling of this film on thepolyester structure, so that no residual film remains on the structureand to avoid the risks of tearing this film during operations ofmanufacture and forming of SMC.

Finally, the uptake of moisture and the water permeability of thesepeelable films should be very low so that the quality of the polyesterresin, which is very sensitive to water, is not impaired duringoperations for the manufacture of SMC, the storage of the polyester orthe forming of SMC.

The prior art described numerous mono- or multilayer films which havebarrier properties and which can be used in the SMC technology, but alsoin other technologies such as fumigation. Patent EP 506515 describesfilms consisting of a polyamide and polyolefin blend for SMC. Patent EP766913 describes the use of films consisting of a polyamide andpolyolefin blend for fumigation. The fumigation of soils consists intreating the soils by injecting gas to a depth of about 0.5 or 1 m andthen the soil to be treated is covered with a film so that the gasremains in the soil for longer, which makes it possible to reduce thequantities of gas to be used. Patent EP 990515 describes a filmcomprising a central polyolefin layer and two outer layers in the formof a polyamide/polyolefin alloy having a surface tension which is onlyslightly different from that of the polyolefin of the alloy. These filmsare useful in the SMC technology and in fumigation. Patent EP 997268describes a mono- or multilayer film comprising metallocene polyethyleneat least a first layer of a polyamide and polyethylene blend, optionallya second polyethylene layer in which the metallocene polyethylene is inthe first and/or in the second layer. These films are useful in the SMCtechnology and in fumigation. None of these documents describespolyamide and polyolefin blends containing nanofillers or their barrierproperties.

It has now been found that the introduction of nanofillers intopolyamide and polyolefin blends led to a much higher increase in thebarrier properties than if the nanofillers were introduced into thepolyamide alone. In other words, if polyamide and polyolefin blends arecompared with the same polyamide and polyolefin blends but containingnanofillers, the increase in the barrier properties is much greater thanif a polyamide is compared with the same polyamide but containingnanofillers. Furthermore, the polyamide and polyolefin blends containingnanofillers are more efficient in real value as a barrier than the samepolyamides containing nanofillers but containing no polyolefin (theproportion of nanofillers relative to the polyamide being the same).These very good barrier properties concern numerous technologies such asfor example SMC, fumigation, expandable polystyrene packaging and airconditioning fluids. The property of a barrier to oxygen is useful infood packaging.

SUMMARY OF THE INVENTION

The present invention relates to polyamide (A) and polyolefin (B) blendscontaining nanofillers in which the polyamide forms the matrix. Theseblends can also be referred to as “polyamide (A), polyolefin (B) andnanofiller blends in which the polyamide forms the matrix”.

The invention also relates to compositions with barrier properties whichare polyamide (A) and polyolefin (B) blends containing nanofillers inwhich the polyamide forms the matrix.

The invention also relates to structures with barrier propertiescomprising at least one layer of these blends and optionally at leastone layer of another material.

The invention also relates to the use of these structures for producinga barrier effect.

These structures are a barrier to numerous fluids, and in particular tooxygen, to styrene, to fumigation fluids, to pentane and to airconditioning fluids.

These structures can be made into bottles, reservoirs, containers, pipesand vessels of all sorts. They can also be converted to films which areused to make packagings. These films are also useful in food packaging,in SMC technology, in fumigation and in expandable polystyrenepackaging. These pipes are useful in air conditioning devices.

The invention also relates to the use of these objects

DETAILED DESCRIPTION OF THE INVENTION

As far as the polyamide (A) and the polyolefin (B) blend containingnanofillers is concerned, the term polyamide refers to the condensationproducts:

-   -   of one or more amino acids, such as aminocaproic,        7-aminoheptanoic, 11-aminoundecanoic and 12-aminododecanoic        acid, or of one or more lactams such as caprolactam,        oenantholactam and lauryllactam;    -   of one or more salts or mixtures of diamines such as        hexamethylenediamine, dodecamethylenediamine,        meta-xylylenediamine, bis(p-aminocyclohexyl)methane and        trimethylhexamethylenediamine with diacids such as isophthalic,        terephthalic, adipic, azelaic, suberic, sebacic and        dodecanedicarboxylic acid.

Examples of polyamides that may be mentioned include PA 6 and PA 6,6.

It is also possible to make advantageous use of copolyamides. Mentionmay be made of the copolyamides resulting from the condensation of atleast two alpha,omega-amino carboxylic acids or of two lactams or of onelactam and one alpha,omega-amino carboxylic acid. Mention may also bemade of the copolyamides resulting from the condensation of at least onealpha,omega-amino carboxylic acid (or one lactam), at least one diamineand at least one dicarboxylic acid.

Examples of lactams which may be mentioned include those having 3 to 12carbon atoms on the main ring, which lactams may be substituted. Mentionmay be made for example, of β,β-dimethylpropiolactam,α,α-dimethylpropiolactam, amylolactam, caprolactam, capryllactam andlauryllactam.

Examples of alpha,omega-amino carboxylic acids that may be mentionedinclude aminoundecanoic acid and aminododecanoic acid. Examples ofdicarboxylic acids that may be mentioned include adipic acid, sebacicacid, isophthalic acid, butanedioic acid, 1,4-cyclohexanedicarboxylicacid, terephthalic acid, the sodium or lithium salt of sulphoisophthalicacid, dimerized fatty acids (these dimerized fatty acids having a dimercontent of at least 98% and preferably being hydrogenated) anddodecanedioic acid, HOOC—(CH₂)₁₀—COOH.

The diamine can be an aliphatic diamine having 6 to 12 carbon atoms; itmay be of aryl and/or saturated cyclic type. Examples that may bementioned include hexamethylenediamine, piperazine,tetramethylenediamine, octamethylenediamine, decamethylenediamine,dodecamethylenediamine, 1,5-diaminohexane,2,2,4-trimethyl-1,6-diaminohexane, diamine polyols, isophoronediamine(IPD), methylpentamethylenediamine (MPDM), bis(aminocyclohexyl)methane(BACM) and bis(3-methyl-4-aminocyclohexyl)methane (BMACM).

Examples of copolyamides that may be mentioned include copolymers ofcaprolactam and lauryllactam (PA 6/12), copolymers of caprolactam,adipic acid and hexamethylenediamine (PA 6/6-6), copolymers ofcaprolactam, lauryllactam, adipic acid and hexamethylenediamine (PA6/12/6-6), copolymers of caprolactam, lauryllactam, 11-aminoundecanoicacid, azelaic acid and hexamethylenediamine (PA 6/6-9/11/12), copolymersof caprolactam, lauryllactam, 11-aminoundecanoic acid, adipic acid andhexamethylenediamine (PA 6/6-6/11/12), and copolymers of lauryllactam,azelaic acid and hexamethylenediamine (PA 6-9/12).

Advantageously the copolyamide is chosen from PA 6/12 and PA 6/6,6.

It is possible to use polyamide blends. Advantageously, the relativeviscosity of the polyamides, measured in solution at 1% in sulphuricacid at 20° C., is between 1.5 and 6.

There will be no departure from the framework of the invention onreplacing part of the polyamide (A) with a polyamide block and polyetherblock copolymer, that is to say on using a mixture comprising at leastone of the previous polyamides and at least one polyamide block andpolyether block copolymer.

The polyamide block and polyether block copolymers result from thecopolycondensation of polyamide sequences having reactive ends withpolyether sequences having reactive ends, such as, inter alia:

-   -   1) Polyamide sequences having diamine chain ends with        polyoxyalkylene sequences having dicarboxylic chain ends.    -   2) Polyamide sequences having dicarboxylic chain ends with        polyoxyalkylene sequences having diamine chain ends obtained by        cyanoethylation and hydrogenation of aliphatic dihydroxylated        alpha-omega polyoxyalkylene sequences called polyether diols.    -   3) Polyamide sequences having dicarboxylic chain ends with        polyether diols, the products obtained being, in this particular        case, polyether-esteramides. These copolymers are advantageously        used.

The polyamide sequences having dicarboxylic chain ends are obtained, forexample, from the condensation of alpha-omega aminocarboxylic acids,lactams or dicarboxylic acids and diamines in the presence of a chainregulator dicarboxylic acid.

The polyether may be for example polyethylene glycol (PEG), apolypropylene glycol (PPG) or a polytetramethylene glycol (PTMG). Thelatter is also called polytetrahydrofuran (PTHF).

The number-average molar mass Mn of the polyamide sequences is between300 and 15 000 and preferably between 600 and 5 000. The mass Mn of thepolyether sequences is between 100 and 6 000, and preferably between 200and 3 000.

The polyamide block and polyether block polymers may also compriserandomly distributed units. These polymers can be prepared by thesimultaneous reaction of the polyether and the precursors of thepolyamide blocks.

For example, it is possible to react polyether diol, a lactam (or analpha-omega amino acid) and a chain regulator diacid in the presence ofa small amount of water. A polymer is obtained which essentially haspolyether blocks, polyamide blocks of widely varying length, but alsothe various reagents having randomly reacted which are randomlydistributed along the polymer chain.

Whether these polyamide block and polyether block polymers are obtainedfrom the copolycondensation of polyamide and polyether sequencesprepared beforehand or from a single step reaction, have for exampleShore D hardness which may be between 20 and 75, and advantageouslybetween 30 and 70, and an inherent viscosity between 0.8 and 2.5,measured in metacresol at 250° C. for an initial concentration of 0.8g/100 ml. The MFIs may be between 5 and 50 (235° C. under a load of 1kg)

The polyether diol blocks are either used as they are andcopolycondensed with polyamide blocks having carboxylic ends, or theyare aminated so as to be converted to polyether diamines and condensedwith polyamide blocks having carboxylic ends. They can also be blendedwith polyamide precursors and a chain regulator in order to makepolyamide block and polyether block polymers having randomly distributedunits.

Polyamide and polyether block polymers are described in patents U.S.Pat. Nos. 4,331,786, 4,115,475, 4,195,015, 4,839,441, 4,864,014,4,230,838, and 4,332,920.

The ratio of the quantity of polyamide block and polyether blockcopolymer to the quantity of polyamide is, by weight, advantageouslybetween 10/90 and 60/40. Mention may be made, for example, of the blendsof PTMG block copolymer and blends of (i) PA 6 and (ii) PA 12 block andPTMG block copolymer.

PA 6, PA 6-6 and PA 6/6-6 are advantageously used.

Regarding the polyolefin (B) of the polyamide (A)/polyolefin (B) blendit may be functionalized or unfunctionalized or may be a blend of atleast one functionalized polyolefin and/or at least one unfunctionalizedpolyolefin. For simplification, functionalized polyolefins have beendescribed (B1) and unfunctionalized polyolefins (B2) below.

An unfunctionalized polyolefin (B2) is conventionally a homopolymer orcopolymer of alpha-olefins or diolefins, such as, for example, ethylene,propylene, 1-butene, 1-octene and butadiene. By way of example, mentionmay be made of:

-   -   the homopolymers and copolymers of polyethylene, in particular        LDPE, HDPE, LLDPE (linear low density polyethylene), VLDPE (very        low density polyethylene) and metallocene polyethylene.    -   the homopolymers or copolymers of propylene.    -   ethylene-alpha-olefin copolymers such as ethylene-propylene,        EPRs (ethylene-propylene rubbers) and ethylene-propylene-diene        monomer copolymers (EPDMs).    -   styrene/ethylene-butene/styrene (SEBS),        styrene/butadiene/styrene (SBS), styrene/isoprene/styrene (SIS)        and styrene/ethylene-propylene/styrene (SEPS) block copolymers.    -   the copolymers of ethylene with at least one product selected        from the salts and esters of unsaturated carboxylic acids, such        as alkyl (meth)acrylate (for example methyl acrylate), or vinyl        esters of saturated carboxylic acids, such as ethylene vinyl        acetate (EVA), it being possible for the proportion of comonomer        to be up to 40% by weight.

The functionalized polyolefin (B1) can be a polymer of alpha-olefinshaving reactive units (the functionalities); reactive units of this kindare acid, anhydride or epoxy functions. By way of example mention may bemade of the above polyolefins (B2) grafted or co- or terpolymerized withunsaturated epoxides such as glycidyl (meth)acrylate, or with carboxylicacids or the corresponding salts or esters, such as (meth)acrylic acid(which can be fully or partly neutralized by metals such as Zn, etc.) orelse with anhydrides of carboxylic acids, such as maleic anhydride. Afunctionalized polyolefin is, for example, a PE/EPR blend whose ratio byweight can vary within wide limits, for example between 40/60 and 90/10,the said blend being cografted with an anhydride, especially maleicanhydride, in accordance with a degree of grafting of, for example, from0.01 to 5% by weight.

The functionalized polyolefin (B1) may be selected from the following(co)polymers, grafted with maleic anhydride or glycidyl methacrylate, inwhich the degree of grafting is, for example, from 0.01 to 5% by weight:

-   -   PE, PP, copolymers of ethylene with propylene, butene, hexene or        octene containing for example from 35 to 80% by weight of        ethylene;    -   ethylene-alpha-olefin copolymers such as ethylene-propylene,        EPRs (ethylene-propylene rubbers) and ethylene-propylene-diene        monomer copolymers (EPDMs).    -   styrene/ethylene-butene/styrene (SEBS),        styrene/butadiene/styrene (SBS), styrene/isoprene/styrene (SIS)        and styrene/ethylene-propylene/styrene (SEPS) block copolymers.    -   ethylene-vinyl acetate (EVA) copolymers containing up to 40% by        weight of vinyl acetate;    -   ethylene-alkyl (meth)acrylate copolymers containing up to 40% by        weight of alkyl (meth)acrylate;    -   ethylene-vinyl acetate (EVA) and alkyl (meth)acrylate        copolymers, containing up to 40% by weight of comonomers.

The functionalized polyolefin (B1) can also be selected fromethylene-propylene copolymers containing a major proportion of propylenewhich are grafted with maleic anhydride and then condensed withmonoamino polyamide (or a polyamide oligomer) (products described inEP-A-0342066).

The functionalized polyolefin (B1) may also be a copolymer or terpolymerof at least one of the following units: (1) ethylene, (2) alkyl(meth)acrylate or vinyl ester of saturated carboxylic acid and (3)anhydride such as maleic anhydride or (meth)acrylic acid or epoxy suchas glycidyl (meth)acrylate.

By way of example of functionalized polyolefins of this last type,mention may be made of the following copolymers, in which the ethylenerepresents preferably at least 60% by weight and in which the termonomer(the function) represents, for example, from 0.1 to 10% by weight of thecopolymer:

-   -   ethylene-alkyl (meth)acrylate-(meth)acrylic acid or maleic        anhydride or glycidyl methacrylate copolymers;    -   ethylene-vinyl acetate-maleic anhydride or glycidyl methacrylate        copolymers;    -   ethylene-vinyl acetate or alkyl (meth)acrylate-(meth)acrylic        acid or maleic anhydride or glycidyl methacrylate copolymers.

In the above copolymers, the (meth)acrylic acid can be in the form of asalt with Zn or Li.

The terms “alkyl (meth)acrylate” in (B1) or (B2) denotes C1 to C8 alkylacrylates and methacrylates and may be selected from methyl acrylate,ethyl acrylate, n-butyl acrylate, isobutyl acrylate, 2-ethylhexylacrylate, cyclohexyl acrylate, methyl methacrylate and ethylmethacrylate.

Furthermore, the abovementioned polyolefins (B1) may also be crosslinkedby any appropriate process or agent (diepoxy, diacid, peroxide, etc.);the term “functionalized polyolefin” also embraces the blends of theabovementioned polyolefins with a difunctional reagent such as diacid,dianhydride, diepoxy, etc. which is capable of reacting with the saidpolyolefins, or the blends of at least two functionalized polyolefinswhich are capable of reacting with themselves.

The abovementioned copolymers, (B1) and (B2), may be copolymerizedrandomly or blockwise and may have a linear or branched structure.

The molecular weight, MFI and density of these polyolefins may also varywithin a wide range, as the person skilled in the art will appreciate.MFI, the abbreviation for melt flow index, is the index of fluidity inthe melt state. It is measured in accordance with the standard ASTM1238.

The unfunctionalized polyolefins (B2) are advantageously selected fromhomopolymers or copolymers of propylene and any homopolymer of ethyleneor copolymer of ethylene and a higher alpha-olefin-type comonomer suchas butene, hexene, octene or 4-methyl-1-pentene. Mention may be made,for example, of PPs, high density PEs, medium density PE, linear lowdensity PE, low density PE and very low density PE. These polyethylenesare known by the person skilled in the art as being products of aradical process, products of Ziegler catalysis or, more recently,products of metallocene catalysis.

The functionalized polyolefins (B1) are advantageously selected from anypolymer containing alpha-olefin units and units which carry polarreactive functions, such as epoxy, carboxylic acid or carboxylicanhydride functions. Examples of such polymers that may be mentionedinclude the terpolymers of ethylene, alkyl acrylate and maleic anhydrideor glycidyl methacrylate, such as the Applicant's Lotader® products, orpolyolefins crafted with maleic anhydride, such as the Applicant'sOrevac® products, and also terpolymers of ethylene, alkyl acrylate and(meth)acrylic acid. Mention may also be made of the homopolymers orcopolymers of polypropylene which are grafted with a carboxylicanhydride and then condensed with polyamides or monoamino polyamideoligomers.

The MFI of (A), and the MFIs of (B1) and (B2), can be selected within awide range; however, in order to facilitate the dispersion of (B) it isrecommended that the viscosities of (A) and (B) be little different.

For small proportions of (B), for example from 10 to 15 parts, it issufficient to use an unfunctionalized polyolefin (B2). The proportion of(B2) and (B1) in the (B) phase depends on the amount of functionspresent in (B1) and on their reactivity. It is advantageous to use(B1)/(B2) weight ratios ranging from 5/35 to 15/25. It is also possibleto use only a mixture of polyolefins (B1) in order to obtaincrosslinking.

The polyamide (A) and polyolefin (B) blend containing the nanofillers ispolyamide matrix-based. Usually, it is sufficient for the proportion ofpolyamide in the polyamide (A) and polyolefin (B) blend containing thecarbon nanotubes to be at least 40% by weight, and preferably between 40and 75%, and even better between 50 and 75% for there to be a polyamidematrix. That is the case for the first three preferred embodiments ofthe polyamide and polyolefin blend. In the fourth preferred embodiment,the polyolefin phase is crosslinked, which ensures that there is nophase inversion and that there is still a polyamide matrix.

In accordance with a first preferred embodiment of the invention, thepolyolefin (B) comprises (i) a high-density polyethylene (HDPE) and (ii)a polyethylene (C1) and a polymer (C2) blend chosen from elastomers,very low-density polyethylenes and ethylene copolymers, the (C1)+(C2)blend being cografted with an unsaturated carboxylic acid or anunsaturated carboxylic anhydride.

According to a variant of this first embodiment of the invention, thepolyolefin (B) comprises (i) a high-density polyethylene (HDPE), (ii) apolymer (C2) chosen from elastomers, very low-density polyethylenes andthe ethylene copolymers (C2) being grafted with an unsaturatedcarboxylic acid or an unsaturated carboxylic acid anhydride and (iii) apolymer (C′2) chosen from elastomers, very low-density polyethylenes andethylene copolymers.

In accordance with a second preferred embodiment of the invention, thepolyolefin (B) comprises (i) polypropylene and (ii) a polyolefin whichresults from the reaction of a polyamide (C4) with a copolymer (C3)comprising propylene and a grafted or copolymerized, unsaturated monomerX.

In accordance with a third preferred embodiment of the invention, thepolyolefin (B) comprises (i) a polyethylene of the EVA, LLDPE, VLDPE ormetallocene type and (ii) an ethylene-alkyl (meth)acrylate-maleicanhydride copolymer.

In accordance with a fourth preferred embodiment of the invention, thepolyolefin comprises two functionalized polymers comprising at least 50mol % of ethylene units and capable of reacting to form a crosslinkedphase. According to one variant, the polyamide (A) is chosen from the(i) polyamide and (ii) PA 6 block and PTMG block copolymer blends andthe (i) polyamide and (ii) PA 12 block and PTMG block copolymer blends;the ratio of the quantities of copolymer and polyamide by weight beingbetween 10/90 and 60/40.

As far as the first embodiment is concerned, the proportions areadvantageously the following (by weight):

-   -   60 to 70% of polyamide,    -   5 to 15% of the cografted (C1) and (C2) blend    -   the remainder as high-density polyethylene.

As far as the high-density polyethylene is concerned, its density isadvantageously between 0.940 and 0.965 and the MFI between 0.1 and 5g/10 min. (190° C. 2.16 kg).

The polyethylene (C1) may be chosen from the polyethylenes mentionedabove. Advantageously, (C1) is a high-density polyethylene (HDPE) havinga density between 0.940 and 0.965. The MFI of (C1) is (under 2.16kg-190° C.) between 0.1 and 3 g/10 min.

The copolymer (C2) may be for example an ethylene/propylene (EPR) orethylene/propylene/diene (EPDM) elastomer. (C2) may also be a very lowdensity polyethylene (VLDPE) which is either an ethylene homopolymer, oran ethylene and an alpha-olefin copolymer. (C2) may also be a copolylmerof ethylene with at least one product chosen from (i) unsaturatedcarboxylic acids, their salts, their esters, (ii) vinyl esters ofsaturated carboxylic acids (iii) unsaturated dicarboxylic acids, theirsalts, their esters, their hemiesters, their anhydrides. Advantageously,(C2) is an EPR.

Advantageously, 60 to 95 parts of (C1) per 40 to 5 parts of (C2) areused.

The (C1) and (C2) blend is grafted with an unsaturated carboxylic acid,that is to say (C1) and (C2) are cografted. There will be no departurefrom the framework of the invention on using a functional derivative ofthis acid. Examples of unsaturated carboxylic acid are those having 2 to20 carbon atoms such as acrylic, methacrylic, maleic, fumaric anditaconic acids. The functional derivatives of these acids comprise forexample the anhydrides, the ester derivatives, the amide derivatives,the imide derivatives and the metal salts (such as the alkali metalsalts) of the unsaturated carboxylic acids.

Unsaturated dicarboxylic acids having 4 to 10 carbon atoms and theirfunctional derivatives, particularly their anhydrides, are particularlypreferred grafting monomers. These grafting monomers comprise forexample maleic, fumaric, itaconic, citraconic, allylsuccinic,cyclohex-4-ene-1,2-dicarboxylic,4-methyl-cyclohex-4-ene-1,2-dicarboxylic,bicyclo(2.2.1)-hept-5-ene-2,3-dicarboxylic,x-methylbicyclo(2.2.1)-hept-5-ene-2,3-dicarboxylic acids, maleic,itaconic, citraconic, allylsuccinic, cyclohex-4-ene-1,2-dicarboxylic,4-methylenecyclohex-4-ene-1,2-dicarboxylic,bicyclo(2.2.1)hept-5-ene-2,3-dicarboxylic, andx-methylbicyclo(2.2.1)hept-5-ene-2,2-dicarboxylic anhydrides. Maleicanhydride is advantageously used.

Various known methods can be used to graft a grafting monomer onto the(C1) and (C2) blend. For example, this may be carried out by heating the(C1) and (C2) polymers at high temperatures, about 150° to about 300°C., in the presence or in the absence of a solvent with or without agenerator of radicals.

In the (C1) and (C2) blend modified by grafting, which is obtained asmentioned above, the quantity of grafting monomer may be chosen in anappropriate manner, but it is preferably from 0.01 to 10%, even betterfrom 600 ppm to 2% relative to the weight of (C1) and (C2) grafted. Thequantity of monomer grafted is determined by assaying the succinicfunctions by FTIR spectroscopy. The MFI of (C1) and (C2) having beencografted is from 5 to 30 g/10 min. (190° C.-2.16 kg), preferably 13 to20.

Advantageously, the cografted (C1) and (C2) blend is such that theMFI₁₀/MFI₂ ratio is greater than 18.5, MFI₁₀ designating the flow indexat 190° C. under a load of 10 kg, and MFI₂ the index under a load of2.16 kg. Advantageously, the MFI₂₀ of the blend of the cografted (C1)and (C2) polymers is less than 24. MFI₂₀ designates the flow index at190° C. under a load of 21.6 kg.

As far as the variant of the first embodiment is concerned, theproportions are advantageously the following (by weight):

-   -   60 to 70% of polyamide,    -   5 to 10% of grafted (C2),    -   5 to 10% of (C′2)    -   the remainder as high-density polyethylene.        (C2) is advantageously an EPR or an EPDM, (C′2) is        advantageously an EPR containing, by weight, 70 to 75% of        ethylene.

As far as the second embodiment of the invention is concerned, theproportions are advantageously the following (by weight):

-   -   60 to 70% of polyamide,    -   20 to 30% of polypropylene

3 to 10% of a polyolefin which results from the reaction of a polyamide(C4) with a copolymer (C3) comprising propylene and a grafted orcopolymerized, unsaturated monomer X.

The MFI of the polypropylene is advantageously less than 0.5 g/10 min(230° C.-2.16 kg) and preferably between 0.1 and 0.5. Such products aredescribed in EP 64781.

A description will now be given of the grafted product of this secondembodiment of the invention. First of all, (C3) is prepared, which iseither a copolymer of propylene and all unsaturated monomer X or apolypropylene onto which an unsaturated monomer X is grafted. X is anyunsaturated monomer which can be copolymerized with propylene or graftedonto polypropylene and possesses a function which is able to react witha polyamide. This function may be, for example, a carboxylic acid, adicarboxylic anhydride or an epoxide. Examples of monomers X that may bementioned include (meth)acrylic acid, maleic anhydride and unsaturatedepoxides such as glycidyl (meth)acrylate. It is advantageous to usemaleic anhydride. As regards grafted polypropylenes, X can be graftedonto polypropylene homopolymers or copolymers, such asethylene-propylene copolymers containing a major proportion of propylene(in moles). Advantageously, (C3) is such that X is grafted. Grafting isan operation which is known per se.

(C4) is a polyamide or a polyamide oligomer. Polyamide oligomers aredescribed in EP 342066 and FR 2291225. The polyamides (or oligomers)(C4) are condensation products of monomers already mentioned above.Mixtures of polyamides may be used. It is advantageous to use PA 6, PA11, PA 12, the copolyamide having 6-units and 12-units (PA 6/12), andthe copolyamide based on caprolactam, hexamethylenediamine and adipicacid (PA 6/6-6). The polyamides or oligomers (C4) may have acid, amineor monoamine end groups. For the polyamide to have a monoamine endgroup, it is sufficient to use a chain regulator of formula

in which:

R₁ is hydrogen or a linear or branched alkyl group containing up to 20carbon atoms and

R₂ is a linear or branched alkyl or alkenyl group having up to 20 carbonatoms, a saturated or unsaturated cycloaliphatic radical, an aromaticradical or a combination of the above. The regulator can be, forexample, laurylamine or oleylamine.

(C4) is advantageously a PA 6, a PA 11 or a PA 12. The proportion of C4in C3+C4 by weight is advantageously between 0.1 and 60%. The reactionof (C3) with (C4) takes place preferably in the melt state. It ispossible, for example, to knead (C3) and (C4) in an extruder at atemperature which is generally between 230 and 250° C. The averageresidence time of the melt in the extruder may be between 10 seconds and3 minutes and, preferably, between 1 and 2 minutes.

As far as the third embodiment is concerned, the proportions areadvantageously the following (by weight):

-   -   60 to 70% of polyamide,    -   5 to 15% of an ethylene-alkyl (meth)acrylate-maleic anhydride        copolymer,

the remainder is a polyethylene of the EVA, ethylene-alkyl(meth)acrylate, LLDPE, VLDPE or metallocene type; advantageously, thedensity of the LLDPE, VLDPE or metallocene polyethylene is between 0.870and 0.925, and the MFI is between 0.1 and 5 (190° C.-2.16 kg).

The ethylene-alkyl (meth)acrylate-maleic anhydride copolymersadvantageously contain from 0.2 to 10% by weight of maleic anhydride andup to 40% and, preferably, from 5 to 40% of alkyl (meth)acrylate. TheirMFI is between 2 and 100 (190° C.-2.16 kg). The alkyl (meth)acrylateshave already been described above. The melting point is between 80 and120° C. These copolymers are commercially available. They are producedby radical polymerization at a pressure which may be between 200 and 2500 bars.

As far as the fourth embodiment is concerned, the proportions areadvantageously the following (by weight):

-   -   30 to 95% of polyamide,    -   70 to 5% of blend of an ethylene-alkyl (meth)acrylate-maleic        anhydride copolymer and of an ethylene-alkyl        (meth)acrylate-glycidyl methacrylate copolymer.

The ethylene-alkyl (meth)acrylate-maleic anhydride copolymersadvantageously contain from 0.2 to 10% by weight of maleic anhydride andup to 40% and, preferably, from 5 to 40% of alkyl (meth)acrylate. TheirMFI is between 2 and 100 (190° C.-2.16 kg). The alkyl (meth)acrylateshave already been described above. The melting point is between 80 and120° C. These copolymers are commercially available. They are producedby radical polymerization at a pressure which may be between 200 and 2500 bars.

The ethylene/alkyl (meth)acrylate/glycidyl methacrylate copolymer maycontain up to 40% by weight of alkyl (meth)acrylate, advantageously from5 to 40% and up to 20% by weight of unsaturated epoxide, preferably 0.1to 12%.

Advantageously, the alkyl (meth)acrylate is chosen from methyl(meth)acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate,2-ethylhexyl acrylate. The quantity of alkyl (meth)acrylate ispreferably from 20 to 35%. The MFI is advantageously between 5 and 100(in g/10 min at 190° C. under 2.16 kg), the melting point is between 60and 110° C. This copolymer may be obtained by free-radicalpolymerization of the monomers.

It is possible to add catalysts in order to speed up the reactionbetween the epoxy and anhydride functions; among the compounds capableof speeding up the reaction between the epoxy function and the anhydridefunction, mention may be made in particular:

-   -   of tertiary amines such as dimethyllaurylamine,        dimethylstearylamine, N-butylmorpholine,        N,N-dimethylcyclohexylamine, benzyldimethylamine, pyridine,        dimethylamino-4-pyridine, methyl-1-imidazole,        tetramethylethylhydrazine, N,N-dimethylpiperazine,        N,N,N′,N′-tetramethyl-1,6-hexanediamine, a mixture of tertiary        amines having from 16 to 18 carbons and known under the name        dimethyltallowamine,    -   tertiary phosphines such as triphenylphosphine,    -   zinc alkyldithiocarbamates,    -   acids,    -   amino acids such as for example 11-aminoundecanoic acid,        aminocaproic acid (obtained for example from the opening of        caprolactam) and 12-aminododecanoic acid (obtained for example        from the opening of lauryllactam).

There will be no departure from the framework of the invention if aportion of the ethylene-alkyl (meth)acrylate-maleic anhydride copolymeris replaced with an ethylene-acrylic acid copolymer or anethylene-maleic anhydride copolymer, the maleic anhydride having beenfully or partially hydrolysed. These copolymers may also comprise analkyl (meth)acrylate. This part may represent up to 30% of theethylene-alkyl (meth)acrylate-maleic anhydride copolymer.

As far as the nanofillers are concerned, they designate particles of anyshape, at least one of their dimensions being in the nanometre range.Advantageously, they are lamellar peelable fillers. In particular, thelamellar peelable fillers are silicates and in particular organophilictreated clays; these clays, which exist in the form of sheets, are madeorganophilic by intercalating organic or polymeric molecules betweenthem, and are obtained in particular according to a process as describedin patent U.S. Pat. No. 5,578,672.

Preferably, the clays used are of the smectite type, either of naturalorigin, such as in particular montmorillonites, bentonites, saponites,hectorites, fluorohectorites, beidellites, stibensites, nontronites,stipulgites, attapulgites, illites, vermiculites, halloysites,stevensites, zeolites, fuller's earth and mica, or of synthetic origin,such as permutites.

By way of example, mention may be made of the organophilic claysdescribed in patent U.S. Pat. No. 6,117,932. Preferably, the clay ismodified with an organic substance by ionic bonding with an onium ionhaving 6 carbon atoms or more. If the number of carbon atoms is lessthan 6, the organic onium ion is too hydrophilic and therefore thecompatibility with the polymer ((A) and (B) blend) may decrease. By wayof example of organic onium ion, mention may be made of hexylammoniumions, octylammonium ions, 2-ethylhexylammonium ions, dodecylammoniumions, laurylammonium ions, octadecylammonium (stearylammonium) ions,dioctyldimethylammonium ions, trioctylammonium ions,distearyldimethylammonium ions, stearyltrimethylammonium ions andammonium laurate ions. It is recommended to use a clay having thehighest possible surface of contact with the polymer. The higher thecontact surface, the greater the separation of the clay lamellae. Thecationic exchange capacity of the clay is preferably between 50 and 200milliequivalents per 100 g. If the capacity is less than 50, theexchange of the onium ions is insufficient and the separation of theclay lamellae may be difficult. By contrast, if the capacity is greaterthan 200, the strength of bonding between the clay lamellae is so strongthat the separation of the lamellae may be difficult. By way of exampleof clay, mention may be made of smectite, montmorillonite, saponite,hectorite, beidellite, stibensite, nontronite, vermiculite, halloysiteand mica. These clays may be of natural or synthetic origin. Theproportion of organic onium ion is advantageously between 0.3 et 3equivalents of the ion exchange capacity of the clay. If the proportionis less than 0.3, the separation of the clay lamellae may be difficult.If the proportion is greater than 3, degradation of the polymer mayoccur. The proportion of organic onium ion is preferably between 0.5 and2 equivalents of the ion exchange capacity of the clay.

As far as the proportion of nanofillers in the polyamide and polyolefinblend is concerned, it may be at any level. The higher this proportion,the better the barrier properties. Advantageously, this proportion isbetween 0.1 and 50 parts per respectively 100 parts of the (A) and (B)blend; and preferably between 0.5 and 10.There will be no departure fromthe framework of the invention on using a blend of nanofillers.

The compositions according to the invention may additionally contain atleast one additive chosen from:

-   -   colorants;    -   pigments;    -   brightners;    -   antioxidants:    -   flame retardants;    -   UV stabilizers.

The compositions of the invention are prepared either by blending allthe ingredients (A, B, nanofillers and optional additive) in theso-called “direct” process, or by adding the nanofillers and theoptional additive to the already prepared A/B blend or else by blendinga polyamide (A) already containing nanofillers with a polyolefin (B) ora polyamide (A) with a polyolefin (B) already containing nanofillers orany combination of these possibilities. The polyamide containingnanofillers may be obtained during, the polymerization of its monomer(or its monomers) in the presence of nanofillers or by compounding thepolyamide and the nanofillers.

Use is advantageously made of the usual blending and kneading devices inthe thermoplastics industry such as extruders and kneaders, for exampleBUSS® cokneaders.

EXAMPLES

-   1—case of permeability to styrene (SMC and BMC application)-   Principle of the method of measurement: permeation cell coupled to a    chromatographic detector allowing the mass of the permeate to be    quantified.-   Permeate: styrene-   Temperature: 40° C.-   Samples: 25 micron films obtained by tubular extrusion-blowing of    film-   Making 3 measurements per type of film.    Results:

The following products were used:

-   PA 6 B4: denotes a PA 6 possessing a relative viscosity (at 1% in    sulphuric acid) of 4.-   PA 6 nanocomposite: denotes Durethan KU2-2601 from Bayer® which is a    PA 6 having a viscosity of 177 to 199 ml/g in accordance with ISO    307 enriched with particles of nanoclays.-   Orgalloy 1: denotes a PA 6 and LLDPE blend compatibilized with an    ethylene-butyl acrylate-maleic anhydride copolymer in the respective    proportions 65/25/10 by weight.-   Orgalloy 1 nanocomposite: denotes a PA 6 nanocomposite and LLDPE    blend compatibilized with an ethylene-butyl acrylate-maleic    anhydride copolymer in the respective proportions 65/25/10 by    weight.-   Orgalloy 2: denotes a blend of PA 6, polypropylene and a    compatibilizer in the respective proportions 60/30/10 by weight. The    compatibilizer is a polypropylene onto which maleic anhydride has    been grafted and which was then condensed with a monoamino PA 6    having a weight-average molar mass of 2 500 g; it is described in    patent U.S. Pat. No. 5,342,886.-   Orgalloy 2 nanocomposite: denotes a blend of PA 6 nanocomposite,    polypropylene and a compatibilizer in the respective proportions    60/30/10 by weight. The compatibilizer is a polypropylene onto which    maleic anhydride has been grafted and which was then condensed with    a monoamino PA 6 having a weight-average molar mass of 2 500 g, it    is described in patent U.S. Pat. No. 5,342,886.

The results of the measurements of permeability to styrene are presentedin Table 1.

TABLE 1 Stream of styrene measured at 40° C. Stream of styrene inMaterials g · mm/m² · 24 h PA 6 B4 0.2 PA 6 nanocomposite 0.13 Orgalloy1 0.2 Orgalloy 1 nanocomposite 0.03 Orgalloy 2 0.25 Orgalloy 2nanocomposite 0.1

Intrinsically, the Orgalloy 1 and 2 nanocomposite products are morebarrier producing than PA 6 nanocomposite. In particular, Orgalloy 1nanocomposite is more than 4 times more barrier producing than the PA 6nanocomposite.

The results are presented in Table 1 and the results are expressed inTable 2 in the form of a gain in permeability. The benefit of thecoupling of the “polyamide and polyolefin blend” and “nanocomposite”technologies is visible in Table 2 which mentions the reduction of thepermeability associated with the nanocomposite effect.

TABLE 2 Reduction of the permeability to styrene associated with thenanocomposite effect. Reduction of permeability Passage from PA 6 to PA6 nanocomposite 35% Passage from Orgalloy 1 to Orgalloy 1 85%nanocomposite Passage from Orgalloy 2 to Orgalloy 2 60% nanocomposite

The reductions of permeability are much higher (factor of 2 to 3) in thecase of the coupling of the “polyamide and polyolefin blend” and“nanocomposite” technologies compared with the case of the nanocompositealone (passage from PA 6 to PA 6 nanocomposite).

1. A composition having barrier properties comprising a blend ofPolyamide (A) and polyolefin (B) wherein said blend containsnanofillers, wherein said polyamide forms the matrix, and wherein saidpolyolefin (B) is selected from the group consisting of an ethylenevinyl acetate (EVA) copolymer containing up to 40 percent by weight ofvinyl acetate, linear low density polyethylene (LLDPE), very low densitypolyethylene (VLDPE), metallocene polyethylene, an ethylene-alkyl(meth)acrylate-maleic anhydride copolymer, and mixtures thereof.
 2. Thecomposition according to claim 1, in which the proportion of nanofillersis between 0.1 and 50 parts per respectively 100 parts of(A) and (B)blend.
 3. An article comprising at least one layer consisting of thecomposition of claim 1, and optionally at least one layer of anothermaterial
 4. The article of claim 3 wherein said article comprises abottle, reservoir, container, pipe, or vessel.
 5. The article of claim 3wherein said article comprises a film.